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[Octave-bug-tracker] [bug #46912] qr not working as described
From: |
John W. Eaton |
Subject: |
[Octave-bug-tracker] [bug #46912] qr not working as described |
Date: |
Wed, 20 Jan 2016 17:01:42 +0000 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Iceweasel/38.2.1 |
Follow-up Comment #8, bug #46912 (project octave):
It looks to me like
[q, r, p] = qr (a)
is equivalent to
[q, r, p] = qr (a, 'matrix')
and that
[q, r, p] = qr (a, 'vector')
just returns p in a vector form such that instead of writing
a * p == q * r
you can write
a(:,p) == q * r
So I don't think that any knowledge of the Fortran libraries is really needed
to implement these features. It's just a matter of accepting 'matrix' as the
default and, for the 'vector' argument, transforming the permutation matrix to
a vector of indices. I believe that's equivalent to writing
find (p) - (0:rows(p):numel(p)-1)'
though I'm sure there's a better way of expressing that in C++ when using the
permutation matrix class. I think it is just the col_perm_vec method in the
PermMatrix class.
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- [Octave-bug-tracker] [bug #46912] qr not working as described, Marco Caliari, 2016/01/16
- [Octave-bug-tracker] [bug #46912] qr not working as described, Lachlan Andrew, 2016/01/18
- [Octave-bug-tracker] [bug #46912] qr not working as described, Marco Caliari, 2016/01/18
- [Octave-bug-tracker] [bug #46912] qr not working as described, Lachlan Andrew, 2016/01/19
- [Octave-bug-tracker] [bug #46912] qr not working as described, Marco Caliari, 2016/01/19
- [Octave-bug-tracker] [bug #46912] qr not working as described, Mike Miller, 2016/01/19
- [Octave-bug-tracker] [bug #46912] qr not working as described, Marco Caliari, 2016/01/19
- [Octave-bug-tracker] [bug #46912] qr not working as described, Lachlan Andrew, 2016/01/20
- [Octave-bug-tracker] [bug #46912] qr not working as described,
John W. Eaton <=
- [Octave-bug-tracker] [bug #46912] qr not working as described, Lachlan Andrew, 2016/01/23
- [Octave-bug-tracker] [bug #46912] qr not working as described, Lachlan Andrew, 2016/01/29